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dimitris78
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Registered: ‎09-13-2019

DDR3/DDR4 controller throughput limitations

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We're looking to instantiate a ddr3/ddr4 controller IP in our design to interface with a 64GB external RAM.

There is a number online for the throughout but looks very low:

https://www.xilinx.com/products/intellectual-property/ddr4.html 

What's the throughput limitation for the controller ?

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dimitris78
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Registered: ‎09-13-2019

It seems that I can instantiate a ddr4 controller (pick LRDIMM on the Basic->Controller options->configuration options menu and select a 128GB memory). It can run at 850ps external clock (1.176GHz), on the user side there is a 1.176/4 GHz clock and a 512-bit interface. So the total throughput is ~150Gbps.

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drjohnsmith
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Registered: ‎07-09-2009
what performance are you looking for ?
is the specified 2667 Mbps as you say very low ?
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dimitris78
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On the range 150-160 Gbps ...

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drjohnsmith
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Assuming you had a 160 bit interface to the chips , that means each data line has to run at 1 Gb/s .... constantly.

Can DDR chips run that fast ?

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watari
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Hi @dimitris78 

 

How many DRAM chips do you accept or put on your PCB ?

It depends on DRAM's bus width and performance of DRAM controller.

 

Best regards,

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dimitris78
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That's unspecified for now, we're just looking to see if there's any limitation on the controller on the FPGA. The requirement is for a total of 64GB at that throughput.

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drjohnsmith
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the controler says 2667 Mbps 

You are going to have to use multiple controlers and banks to reach your data rate,

 

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dimitris78
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Registered: ‎09-13-2019

It seems that I can instantiate a ddr4 controller (pick LRDIMM on the Basic->Controller options->configuration options menu and select a 128GB memory). It can run at 850ps external clock (1.176GHz), on the user side there is a 1.176/4 GHz clock and a 512-bit interface. So the total throughput is ~150Gbps.

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drjohnsmith
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Registered: ‎07-09-2009

I notice you have closed this thread,

good luck,

you are going to be seriosuly disapointed if you think you are going to get 150 Gb/s speed with a DDR memory

 

 

 

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